Variation in maturity among oats varieties and its implications for integration into the highland farming systems

Fekede Feyissa

Abstract

This paper presents the
variation in maturity among 20 oats (Avena sativa L.)
varieties assessed in terms of the durations required by the varieties to attain
different physiological growth stages (boot, heading, milk, soft dough and grain
maturity stages). The intention was to analyze the practical implications of
differences in maturity among the varieties in view of peculiarities of the
different farming systems and the various aspects of oats utilization in the
highlands of Ethiopia.

There was marked
variation among the varieties with respect to the durations required to attain
the different growth stages. Taking the soft dough stage as a reference
physiological maturity stage for forage harvest, there was on average a
difference of 31 days between the early (117 days:
Coker SR res 80 SA 130) and late maturing varieties
(148 days: Grayalgeris). The study also revealed that
most of the difference in maturity among the varieties was attributed to
differences in the durations of the vegetative growth
period (planting to heading) than the grain filling period. This feature has
important practical implications for making proper choice of the varieties for
successful integration into the farming system and feed production.

In general, the
variation in maturity among the oats varieties allows the producers to grow the
proper variety according to the farming system and intended purpose of
production. Accordingly, early maturing varieties could be preferably grown as
precursor crops to chickpea/lathyrus, to make efficient use of the small amount
of moisture during belg cropping and in cases where cut-and-carry feeding is
targeted to curb feed shortage during the main rainy season. On the other hand,
late maturing varieties could be the better choice in cases where hay making and
preservation for dry season is targeted.

Keywords: Duration,growth stage, farming system, oats

Introduction

Oats (Avena sativa L.) is a well-adapted fodder crop
grown for a long period of time in the highlands of Ethiopia. It is produced by
some peri-urban dairy cattle producers and by smallholder farmers who own
crossbred dairy cows. Its grain also makes part of the staple diet of human
beings in some parts of central highlands of the country (Lulseged G H
1981). Oats being an annual forage crop is highly useful for integration into
the prevailing mixed crop- livestock farming systems of the highlands on
accounts of its short-term yielding characteristics, use in overcoming seasonal
feed shortages, convenience in crop rotations and its fodder conservation
characteristics. Moreover, farmers can easily grow it because its husbandry is
similar to that of other cereals such as barley and wheat.

There are various cropping systems in the highlands of
Ethiopia including double cropping within a season, rotational cropping and belg
cropping all of which offer potential niches for integrating oats into the
system. Similarly, oats has got different forms of utilization especially with
respect to livestock feed (grazing, cut-and-carry green feeding, hay, silage and
also as a source of cash income through sale of the green material). The grain
aspect for human consumption is also an important dimension which deserves
attention in oats utilization. The variation in maturity among the oats
varieties has got a marked practical significance in view of peculiarities of
the different cropping systems and the various aspects of oats utilization.
However, previous recommendations on oats were made based on some general
aspects of the varieties mainly environmental adaptation and herbage yield
without an in depth information on other features of practical significance such
as maturity. Therefore, this paper is aimed at assessing the variation in
maturity among 20 oats varieties and highlights its practical implications for
integration into the highland mixed farming systems.

Materials and methods

Experimental site

The experiment was conducted at Holetta Agricultural Research
Center (HARC) in the central highlands of Ethiopia. The center is located at 38°30`E, 9°
3`N and 30 km west of Addis Ababa and lies at an elevation of 2400 m above sea
level. Based on an average meteorological data of 34 years (1969 – 2003) of the
HARC, the annual rainfall of the area is 1066 mm with bimodal distribution, over
70% of which occurs during the main rainy season (June to September) and 30%
during the small rainy season (February to April). The average annual minimum
and maximum temperatures of the area are 6°
to 22°C.
The area is also characterized by occasional frost that occurs in the months of
October to December, where temperatures below zero are recorded for few days
during these months.

The major soil type of the area is a red-brown clay loam
nitosol, and analysis of composite soil sample taken from the upper 20 – 30 cm
soil horizon of the specific experimental plot in this study indicated that the
soil had a pH (1:1 H2O) of 5.1, total N content of 0.2%, P content of
12.4 ppm, OM content of 2.2% and cation exchange capacity (CEC) of 17.0 meq/100
g soil. Similarly, values for the major climatic variables during the course of
the experimental period (June – December 2003) were: total rainfall (686 mm),
average minimum and maximum temperatures (6.5°
and 21.2°C)
and relative humidity of 60.6% (HARC meteorological data).

Oats varieties

Twenty oats varieties that were
selected on the basis of their adaptation to the highlands of Ethiopia from
previous introduction and screening works were used for the experiment. The
varieties and their respective origins are shown in Table 1.

Table 1.
Varieties of oats used in the study

Serial No

Variety

Origin

1

79 Ab 382 (TX) (80 SA
94)

CIMMYT

2

79 Ab 384 (TX) (80 SA
95)

CIMMYT

3

CI – 8251

Yugoslavia

4

Jasari

Kenya

5

SRCP X 80 Ab 2806

CIMMYT

6

Lampton

Ethiopia

7

SRCP X 80 Ab 2252

CIMMYT

8

CI – 8235

USA

9

CI – 8237

USA

10

Grayalgeris

Algeria

11

SRCP X 80 Ab 2291

CIMMYT

12

Coker SR res 80 SA 130

CIMMYT

13

SRCP X 80 Ab 2764

CIMMYT

14

SRCP X 80 Ab 2767

CIMMYT

15

Clintland 60 MN 16016

CIMMYT

16

PI – 338517

Not specified

17

PI – 244475

Not specified

18

PI – 5800

Not specified

19

PI – 244480

Not specified

20

Ky to 78394 Canada

CIMMYT

Sowing, data collection and measurements

The varieties were sown on 24th of June 2003 in a
Randomized Complete Block Design (RCBD) with four replications. Sowing was made
by drilling the seeds in rows of 0.2 m wide on 4m x 3m plots spaced 0.5 m apart.
A starter dose of fertilizer at the rate of 18/46 N/P2O5
kg/ha (100 kg DAP/ha) was applied to all plots at sowing. A uniform seeding rate
of 100 kg/ha was used for all the varieties as per previous recommendation for
pure stand of oats in the highlands of Ethiopia (Astatke 1979). All the plots
were hand weeded once, a month after sowing and thereafter as required based on
occurrence of weeds.

The varieties were closely examined beginning from the early
vegetative growth and a reliable record of the different growth stages (boot,
heading, milk, soft dough and grain maturity stages) was taken. The durations
required by each variety to attain the different growth stages were determined
as the period in days from sowing to the respective stages.

Definitions of the terms used to describe the different
growth stages are stated below:

Boot stage – the growth stage of grasses in which the head is
enclosed by the sheath of the upper most (flag) leaf.

Heading stage – the growth stage when the panicle emerges out
of the flag-leaf sheath.

Milk stage – stage during which a white, milk like fluid can
be squeezed from the developing kernel.

Dough stage – stage during which the material pressed out of
the kernel is no longer a liquid but has the consistency of dough.

Grain maturity – stage during which the plant has become
completely yellow, dry and brittle and the kernel is hard.

Statistical analysis

Analysis of variance was performed using the statistical
analysis system (SAS) software (SAS 2001) and mean separation was carried out
using the Duncans new multiple range test.

The following general linear model was used for the analysis:

Yij
= m
+ Bi + Oj+ Eij

Where,

Y – the measured response

m
- the overall mean

Bi – effect of the ith
block

Oj – effect of the jth
oats variety

Eij – the error term associated with each Yij

Results and discussion

The durations required by each oats varieties to attain the
different growth stages are shown in Table 2.

abc means with different
letters within a column are significantly different (P<0.05)

The result indicated that on average the varieties require a
range of 71 to 102 days, 82 to 117 days, 100 to 129 days, 118 to 149 days and
156 to 187 days to attain boot, heading, milk, soft dough and grain maturity
stages, respectively. Coker SR res 80 SA 130, SRCP X 80 Ab 2252, SRCP X 80 Ab
2806, 79 Ab 382 (TX) (80 SA 94), Clintland 60 MN 16016, SRCP X 80 Ab 2291 and Ky
to 78394 Canada were significantly earlier (P<0.05) than most of the varieties
and on average require 71 to 75 days to attain boot stage. On the other extreme,
Grayalgeris and PI – 338517 were significantly late (p<0.05) to attain boot
stage than all the other varieties. Likewise, CI – 8251, PI – 244475 and PI –
5800 were significantly late (P<0.05) than most of the varieties, but
significantly earlier (P<0.05) than Grayalgeris and PI – 338517 to attain a boot
stage. Varieties that require short durations to attain boot stage may be useful
to provide cut-and-carry fodder early as per the requirement of the farming
system. The earliness trait can be further exploited by early sowing and
fertilizer application. The trend in days to boot was also reflected in the
durations of the subsequent growth stages. Accordingly, Grayalgeris and PI –
338517 were significantly late (P<0.05) to attain head, milk, soft dough and
grain maturity stages than all the other varieties, while Coker SR res 80 SA 130
and SRCP X 80 Ab 2252 were significantly earlier (P<0.05) in achieving these
stages.

The wide range of variations recorded among the oats
varieties to attain the different growth stages could allow a sound
classification of the varieties as very early, early, medium, late and very late
in maturity. Taking the soft dough stage as a reference stage for forage
harvesting, Coker SR res 80 SA 130 and SRCP X 80 Ab 2252 can be classified as
very early maturing varieties, whereas Grayalgeris and PI – 338517 can be
categorized as very late maturing varieties. Similarly, varieties such as SRCP X
80 Ab 2291, 79 Ab 384 (TX) (80 SA 95), SRCP X 80 Ab 2806, 79 Ab 382 (TX) (80 SA
94) and PI – 244480 could be categorized as early maturing varieties, while CI –
8251, PI – 5800, PI – 244475 and CI – 8235 can be classified as late maturing
varieties. The rest varieties can be categorized as medium maturing. The
variation in maturity among the oats varieties affects timing of harvest, which
in turn may affect forage yield and quality. Moreover, it is a good indication
of the range of options available for utilization of oats according to priority
and nature of the different farming systems. For instance, early maturing
varieties can progress through different development stages at a faster rate
than late maturing varieties and may be useful for double cropping system in
chickpea/Lathyrus growing highland areas where the chickpea/Lathyrus is grown
using residual moisture in October. Varieties with such quality are highly
preferable in improved forage adoption efforts because they can be introduced
without disturbing the farming system and enable the farmer to get an added
benefit from the same plot of land. On the other hand, late maturing varieties
may help to extend the period of green feed availability and also could be
useful to be preserved as hay for periods of feed shortage.

Hellewell et al (1979) attested that the major
difference in maturity among oats cultivars relate to differences in the length
of the vegetative growth stage (sowing to heading), not the grain filling period
(heading to grain maturity stage) and thus the fast growth of early maturing
cultivars is explained in terms of a shortened vegetative growth stage rather
than a shortened grain filling period. They also reported that the length of
grain filling period is not associated with the relative maturity of any given
cultivar as the latest maturing cultivar could have the shortest grain filling
period. The result of the present study also agrees with the above finding in
that the duration required for vegetative development (shown in Table 3) ranged
widely from 82 to 117 days, while the duration of grain filling period ranged
from 64 to 80 days among the 20 oats varieties. Moreover, late maturing
varieties tended to have comparatively shorter grain filling period than early
maturing varieties.

abc means with different
letters within a column are significantly different (P<0.05)

The choice of which oats variety to grow for silage or hay,
and the decision whether to harvest at the boot or dough stage are dependent on
the resources available for production and the purpose for which the forage is
being grown. Moreover, weather conditions and cropping patterns may dictate when
the forage must be planted and when it must be harvested. With those
constraints, the objective is to choose a variety and harvest stage to maximize
the value of the harvested forage pertaining to its intended use. Collar and
Aksland (2001) suggested that for silage and hay, the boot and dough stages are
two key stages for evaluating, choosing and managing varieties of small grain
forages. On account of their superior combination of yield and digestibility
compared to other stages of development, boot and soft dough stages are the two
recommended stages at which to harvest for silage and hay, respectively. The
boot stage has been reported to be significantly higher in digestibility and
protein than dough stage, but significantly lower in yield (Collar and Aksland
2001). The choosing of boot harvest versus dough harvest should include
comparing the best variety for boot stage versus the best variety for dough
stage, not necessarily the boot versus dough stage for any one variety. Fohner
(2002) suggested that the best varieties for boot stage harvest are high
tillering varieties that are late maturing and produce dense leafy growth, while
the best choice for dough stage harvest are early maturing varieties with a high
grain yield and high grain to stem ratio. But under Ethiopian context, early
maturing varieties may be preferred for boot stage harvest and late maturing
varieties for dough stage harvest. This may enable to obtain a double harvest
from re-growth of the early maturing varieties and in the case of late maturing
varieties, weather conditions may be conducive for hay making by the time they
attain physiological maturity for harvest. Moreover, the prevailing livestock
feed situation in the country demands oats varieties that attain a given
harvestable stage for cut-and-carry feeding during the main rainy season and
those with longer growth duration with high eventual forage yield for
preservation as hay for the dry season. Early maturing oats varieties are also
useful to be grown in combination with vetch as they mature in synchrony with
the companion legume. Curing oats as silage has not been much experienced in the
country, but there is a need to demonstrate silage making as one option of
extending its utilization at least at government institutions. Similarly,
although some farmers preserve oats hay, the variety they are producing, the
extent of utilization and whether they harvest the crop at the recommended stage
for hay is not known and requires further assessment.

Practical implications of the
variation in maturity

From double cropping point of
view

Land shortage for sole cropping
of a forage crop has been one of the bottlenecks for wide adoption of improved
forage crops despite critical livestock feed shortage in mixed farming systems
of the highlands. One of the feasible options for introducing improved forages
into the system could be through integrating feed production with the cropping
venture. Intercropping, rotational and/or double cropping within a season are
some of the available mechanisms for feed-food crops integration. A considerable
portion of land is used for growing chickpea and/or lathyrus using residual
moisture in most of the highland vertisol areas. Traditionally, farmers in such
areas usually plough the land once in June and leave it aside until the planting
time of chickpea and/or lathyrus around mid September to early October. Growing
early maturing oats varieties as a precursor to the main crops (chickpea and
lathyrus) could help to optimize land productivity (in terms of feed and food
production) through double cropping within a season. Highland farmers usually
face critical feed shortage during the main rainy season (mainly around August
and September) as the available land is covered with crops and the conserved
feed reserve is exhausted. Introducing early maturing oats varieties could help
to curb the feed shortage gap without competing with food crops for land in such
areas.

Figure 1. Farmers
harvesting and drying oats while preparing the land for chickpea
production/double cropping
in the Ethiopian highlands

From belg (short rainy
season) cropping point of view

Belg cropping using the short
rains (February to May) is common in some highlands of Ethiopia. Since belg rain
is usually short, erratic and uneven, looking for crop verities that could make
use of and responsive to the small amount of available moisture is the best
strategy for belg growing areas. Oats is one of the preferred crops grown for a
dual-purpose use (food and feed) in such areas. Farmers are very strategic in
using oats during the belg season such that:

i)if the belg rain extends for long and the
moisture is felt adequate for grain setting and normal maturity, the farmers
maintain and manage the oats for grain production.

ii)if the belg rain is inadequate to carry the
crop to physiological maturity for grain, the farmers divert to use as livestock
feed through cut-and-carry feeding system. Green oats marketing for feed is also
common by farmers in which an estimated 2kg of green material (0.5 kg DM) costs
1 Ethiopian Birr with spatial and temporal variations. Based on this estimate,
about 16, 000 Ethiopia Birr (an equivalent of about 1454 USD) could be obtained
from green oats grown on a hectare of land with an estimated average forage
yield of 8 t DM/ha. The fact that oats could be grown on a land marginal for
growing other crops allows the farmers to make efficient use of the less fertile
land with considerable economic gain.

The above scenario of using oats
during the belg season could be further optimized through proper exploitation of
varietial differences in maturity.

From utilization point of
view (cut-and-carry feeding Vs hay making)

The variation in maturity of the
oats varieties would allow farmers and other users to make the proper choice
according to their intended use. For instance, early maturing varieties could
mature for forage during times when weather conditions are not conducive for hay
making such as during the main rainy season. Moreover, most highland areas of
Ethiopia encounter critical feed shortage during the main rainy season (July,
August and September) concomitant to exhaustion of conserved feed (crop residues
and hay) and coverage of the available land with crops. In view of this, growing
early maturing oats varieties could be an ideal strategy to improve livestock
feed supply through cut-and-carry feeding. This significantly help smallholder
farmers for maintaining in-door fed crossbred milking cows and working oxen
which have less access to roam around and fetch feed. On the other hand, when
the intention is hay making and feed conservation, medium or late maturing
varieties will be the proper choice by farmers.

From labour distribution
point of view

In the highland areas where oats
is grown for human food, the varieties which mature earlier than barley are
preferred by farmers as labour required for harvesting and threshing operations
do not coincide with that of barley. Moreover, early maturing oats varieties are
well acknowledged by the farmers due to the fact that they could mature earlier
than barley and provide them with a food grain early when they are needy.

Conclusion

The variation in maturity among the oats varieties allows the
producers to grow the proper variety according to the farming system and
intended purpose of production. Accordingly, early maturing varieties could be
preferably grown as precursor crops to chickpea/lathyrus, to make efficient use
of the small amount of moisture during belg cropping and in cases where
cut-and-carry feeding is targeted to curb feed shortage during the main rainy
season. On the other hand, late maturing varieties could be the better choice in
cases where curing hay and preservation for dry season feeding is targeted. To
this effect, subsequent works need to be done to create farmers awareness on
merits associated with different maturity classes and their applications within
the different farming systems and intended uses.

Acknowledgements

I would like to acknowledge the
financial support by the Agricultural Research and Training Project (ARTP) of
the Ethiopian Agricultural Research Organization (EARO). We are also grateful to
the staff of Feeds and Nutrition Research Program at Holetta Agricultural
Research Center for their keen cooperation during the field work.